Rolling mill control apparatus



Dec. 13, 1966 Filed Feb. 20, 1964 REID ROLLING MILL CONTROL APPARATUS OFF-SET 2 Sheets-Sheet 1 Oh r V (9 INVENTOR grren Reid ATTORNEY Dec. 13, 1966 W. REID ROLLING MILL CONTROL APPARATUS 2 Sheets-Sheet 2 @5 O 72 60 (11 2 TENSION LOAD LOAD REFERENCE 2s INDICATOR INDICATOR CIRCUIT J as {I SlGNA L GATE ENTEGRATOR as "F f VT SIGNAL 70 COMPARISON Vs f CIRCUIT SIGNAL COMPARISON CIRCUIT VAT X-RAY X-RAY GAUGE GAUGE i I4 (9 T l l N l I 92 l I 9| 5 TENSION TENSION SENSING SENSING DEVICE DEVICE United States Patent Ofiice 3,290,912 ROLLING MILL CONTROL APPARATUS Warren Reid, Pittsburgh, Pa, assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., :1 corporation of Pennsylvania Filed Feb. 20, 1964, Ser. No. 346,270 5 Claims. (Cl. 72-9) The present invention relates in general to control apparatus for a strip workpiece rolling mill, and more particularly to strip workpiece tension control apparatus operative with a rolling mill.

The performance of multi-stand tandem rolling mills is determined in part by the respective strip tensions between the various stands of the rolling mill. If the tension in the strip between a given pair of stands is too low, the rolling mill may not track properly such that the strip workpiece will tend to move across the face of the work rolls. If the tension is too high in the strip between a given pair of work stands, the strip may break or in the case of hot mills the strip may neck down or decrease in width and result in the need for excessive trimming of the delivered strip workpiece and consequent increase in scrap. Wide variations in the inter-stand tensions result in detrimental effects on the strip gauge or shape and may possibly result in poor surface characteristics.

Many rolling mills at the present time are operated without special tension control equipment for indicating or controlling the inter-stand tension of the strip workpiece between the given stands. It is left to the mill operator to visually look at the strip workpiece between the roll stands, and make manual adjustments to obtain the desired tensions which in his judgment are reasonable and proper. Hot strip mills installed in recent yea-rs have been equipped with special devices to indicate or exert some degree of control on the inter-stand tension, such as tensiometers or loopers. The tensiometer measures the force in the strip as it passes over the rotating tensiometer roll, and is essentially a spring scale in which the vertical force exerted is a function of the strip workpiece tension.

The looper measures the deviation in the pass line from some preselected value and is essentially a roll supported by a torque a-rm driven from some external source of power. The external source of power for the looper may be pneumatic or hydraulic or may be electrical in the form of a torque motor or an eddy current coupling device. Both the tensiometer and the looper have been applied with varying degrees of success. Each of the latter dcvices has certain inherent disadvantages, with some common to both devices, such as requiring contact with the strip which could mark the strip surface, and being vulnerable to damage in the event of a cobble. Both devices require adjustment in pass line height following a .roll change in the mill, and the output signal from either device is affected by the weight of the strip and the bending force required to bend the strip at each stand as well as over the deflecting roll itself. In addition, both devices are rather expensive.

With the present day emphasis on hot strip mills to run at higher speeds and produce greater tonna-ges of higher quality strip, it is highly desirable to have an inter-stand tension measuring and control apparatus which would be compatible with modern control techniques and would better eliminate or minimize some of the above mentioned disadvantages of the tensiometer and looper devices.

It is an object of the present invention to provide an improved and less expensive strip workpiece tension control apparatus wherein a more accurate measurement of strip workpiece tension is obtained with no contact on the strip surface by the tension measuring device being required and a more rapid following of transient tension changes being realized.

3,29%,912 Patented Dec. 13, 1966 It is a different object of the present invention to provide improved inter-stand strip workpiece tension sensing and control apparatus that is more compatible with modern control techniques and enables a desired operation of the strip workpiece rolling mill at higher speeds and with better accuracy of operation.

In accordance with the present invention, a noncontactin-g inter-stand tension sensing and control apparatus is provided which employs a roll force sensing device or transducer. The roll force transducer is mounted between the frame of a given roll stand and at least one of the rolls, such as a work roll or a back-up roll, in such a manner that it measures a portion of the effective strip horizontal or tension force acting on that particular roll stand. It is intended here to cover the provision of roll force transducers on either the entry or delivery side of the mill stand or both and associated with either the work rolls or the back-up rolls or both. The roll force transducer is operative to provide a first control signal when the strip workpiece is operative with the particular stand N of interest and has not yet become operative with the next succeeding stand N+l or tension providing device, and is thereafter and subsequently operative to provide a control signal including the rolling load on the particular stand N of interest plus the forward tension between stand N and the next succeeding stand N+1 minus the back tension between stand N and the preceding stand N-1. In this way a control signal is provided as a function of the actual forward tension in the strip workpiece and is compared with a reference or desired tension to provide a forward tension error signal that is available for correcting the operative speed of stand N or other stands associated therewith or the operation of strip tension determining devices operative with stand N as may be desired.

The above objects and advantages and the operation of the present invention will become more readily apparent from the following description and accompanying drawings, in which:

FIGURE 1 shows a four high rolling mill having top and bottom work rolls and top and bottom back-up rolls operative with a strip workpiece;

FIG. 2 is a general showing of the present tension control apparatus for a tandem rolling mill;

FIG. 3 is a schematic showing of control apparatus in accordance with the teachings of the present invention; and

FIG. 4 is a diagrammatic showing of the roll forces involved when a strip workpiece passes through the cooperating rolls of a given rolling mill stand.

In FIG. 1, there is shown a rolling mill stand 10 including a top work roll 12, a bottom work roll 14, a top backup roll 16 and a bottom back-up roll 18. A workpiece 20 is passed through and between the work rolls 12 and 14 in a direction from the left toward the right as viewed in FIG. 1. The rolling mill stand 10 includes a frame 22 and a force sensing transducer 24 mounted between the frame 22 and the chock 26 operative with the top work roll 12 and the top back-up roll 16. A similar force transducer 28 is mounted between the frame 22 and the chock 3th for the bottom work roll 14 and the bottom back-up roll 18. Thusly, the provided roll force sensing transducers 24 and 28 will sense and measure the horizontal forces applied between the respective back-up rolls 16 and 18 and the stand frame 22 and will measure the net strip tension force. This net strip tension force includes the horizontal component of the roll force at the roll bite and indicated by the arrow 32 plus the force due to forward tension and indicated by the arrow 34 minus the force due to back tension and indicated by the arrow 36. The actual roll force at the roll bite is illustrated by the arrow 38, and it has a horizontal component illustrated by the 3 arrow 32 and a vertical component shown by the arrow 40.

In FIG. 2 the work rolls 12 and 14 for the stand N are shown operative with the strip 20. The force sensing transducers 24 and 28 are shown operative in a diagrammatic manner with the respective work rolls 12 and 14 and provide a net inter-stand tension force signal to the tension control apparatus 50 in accordance with the net actual tension in the strip workpiece 20 between the stand N and the succeeding stand N+1. Similar force sensing transducers are provided for each of the illustrated stands N-2, N-l, N, and N+1 and respectively provide net inter-stand tension signals between the respective stands N1 and N2, N1 and N, N and N+1, and finally if desired between the stand N+1 and the wind-up reel 52. The tension control apparatus 50 is operative to provide error correction signals to the respective drive motors, or provided screwdown devices if desired, for the illustrated stands operative with the strip workpiece 20. Within the tension control apparatus will be included a reference tension signal source for each of the inter-stand tensions, and a signal comparison device to provide the required tension error signal therefrom.

In FIG. 3 there is schematically shown control apparatus in accordance with the teachings of the present invention for providing a control signal suitable for controlling the inter-stand tension between any given stand and the next adjacent stand. In this regard the roll force sensing transducers 24 and 28 operative with stand N are shown to provide a signal in accordance with the average actual force provided between the respective top and bottom rolls and the frame 22 of the rolling mill stand 10. A load indicator 60 for stand N is provided and may comprise a vertical roll force sensing device or a hot metal detector or the like. A load indicator 62 is operative with the succeeding stand N+1. A signal conductive gate circuit 64 receives the average force signal from the transducers 24 and 28 and is responsive to the load indicator 60 to become conductive for this signal when the strip workpiece is passing through the stand N and has not yet reached the stand N +1. An operational amplifier type of signal integrator 66 is operative to integrate this signal and provide an output in accordance with the horizontal force component illustrated by the force arrow 32 shown in FIG. 1 and existing until the head end of the strip workpiece enters the next succeeding stand N +1, at which time the load indicator 62 closes the gate 64. The signal integrator 66 is now operative to hold the same output for the remainder of the strip workpiece. The output tension signal V now provided and existing at this time is in accordance with the rolling load signal V on stand N minus the back tension signal V between stand N and the preceding stand N 1. Thusly,

During the time interval that the head end of the strip workpiece is moving from stand N to the next succeeding stand N +1, there is zero tension in the strip workpiece between the stand N and the next succeeding stand N +1. Therefore, the force signal from the transducers 24 and 28 includes only the horizontal component of the roll force as shown by the force arrow 32 in FIG. 1 and the force due to the back tension between the stand N and stand N-l as shown by the arrow 36 in FIG. 1.

A signal comparison circuit 68 is provided to effect a difierence between the output tension signal V provided when the head end of the strip is moving from stand N to stand N-i-l and the force signal V provided from the transducers 24 and 28 after the head end of the strip workpiece has passed through and entered the next succeeding stand N+1 such that the force due to the forward tension in the strip workpiece is now a factor. Thusly, the actual tension signal V equals V -V The actual tension output signal V from the signal comparison circuit 68 is in accordance with the actual tension in the strip workpiece between the stand N and the next succeeding stand N 1, and therefore the signal Vf now provided from the transducers 24 and 28 minus the output signal V from the signal integrator 66. This signal V is proportional to the actual inter-stand strip tension as long as the horizontal component of the roll force at the roll bite remains substantially constant. It should be noted that this horizontal component of the roll force may change slightly due to temperature changes in the strip workpiece or slight changes in input thickness of the strip workpiece supplied to stand N, however the net effect would be a change in a direction to maintain the output strip shape and gauge substantially constant relative to stand N. A second signal comparison circuit is provided to compare a desired or reference inter-stand tension in accordance with a signal V provided from a tension reference circuit 72 and the output signal V from the signal summing circuit 68. A tension reference circuit 72 is manually adjustable and permits the operator to set a voltage signal V proportional to the desired tension in the strip workpiece between the stand N and the stand N+1. Thusly, the voltage V is proportional to the desired tension and the voltage V is proportional to the actual tension in the strip workpiece and these are compared in the signal comparison circuit 70 to provide a difierence or error signal V in accordance with any error in the strip tension between the stand N and the stand N+1 to control the respective operational speed of the stand N and/or stand N+1 and to regulate for zero tension error output from the signal comparison circuit 70.

In FIG. 4 there is shown a diagrammatic illustration of a modification of the present control apparatus wherein a vertical roll force transducer is provided and operative with the Work rolls 12 and 14 to sense the vertical component 40 of the roll force at the roll bite instead of the previously measured horizontal component 32 of the roll force 38. The vertical force component F shown by the arrow 40 and the horizontal force component F shown by the arrow 32 comprise the total forces on the strip workpiece 20 at the roll bite. If the work rolls 12 and 14 are initially operated such that the strip workpiece 20 is passed from a preceding stand through the work rolls 12 and 14 to a succeeding stand, a tension sensing device 91 in the form of a conventional tensiometer can be momentarily employed to measure the force due to the forward tension in the strip workpiece 20 and a similar tension sensing device 92 can be momentarily employed to measure the opposing force due to back tension. In this way a determination of the horizontal component force F for a given rolling mill operation can be determined. The force F bears a definite relationship to the vertical component F and is influenced by the roll radius as well as the incoming and outgoing thicknesses for a particular stand. Thusly, the output signal for the vertical force sensing transducer 80 in accordance with the vertical roll force measurement can be utilized to provide a predetermined relationship control signal proportional to thehorizontal component force, in view of the angle 06 between the vertical force component F of the total roll force at the roll bite shown by the arrow 38.

After this initial and momentary determination of the horizontal force component F of the roll force at the roll bite, control apparatus similar to that shown in FIG. 3 and including a signal comparison circuit 70' may be operative with the tension reference circuit 72 for providing a tension error signal relative to the strip workpiece extending between the particular stand as shown in FIG. 4 and the next adjacent stand.

Thusly, I have described control apparatus for providing a control signal in accordance with the actual tension in the strip workpiece between a rolling mill stand and the next adjacent or succeeding stand or the next succeeding strip tension providing device which may include a strip workpiece wind-up reel or the like.

In reference to the control apparatus shown in FIG. 4 the horizontal component force P is substantially equal to the force F times the tangent of the angle a. It is here assumed that the total roll force shown by the arrow 38 is acting at substantially the mid-point of the arc of contact of the work roll 12 with the strip workpiece 20. The horizontal component force F is equal to the measured vertical component force F times one-half the square root of the input thickness h minus the output thickness I1 divided by the radius R of the work roll 12. Thusly, the formula for this relationship would be:

1 V F =F tan This can readily be established by the trigonometric relationship between the horizontal and vertical components of the roll force shown by the arrow 38.

In the operation of the control apparatus in accordance with the present invention and shown in FIG. 3, a first control signal V is provided through the operation of the gate circuit 64 and the operational amplifier signal integrator 66 in accordance with the signal V for the horizontal component of the rolling load on stand N minus the signal V for the back tension between stand N and stand N -1. During the time interval when the head end of the strip workpiece is moving from stand N to the next succeeding stand N +1, there is zero forward tension in the strip workpiece between stand N and stand N +1, and it is during this interval that the gate circuit 64 is held open to provide the desired output signal V from the signal integrator 66. The gate circuit 64 is controlled by load signals which may be in the form of load relay signals or a signal from one of the force sensing transducers of the given rolling mill stand. The gate circuit 64 is closed when the strip workpiece head end reaches the next succeeding rolling mill stand, to cause the signal integrator 66 to now hold the output signal V for the duration of the passage of the remainder of the particular strip workpiece. The signal comparison circuit 68 is operative to provide a difference signal Vat in accordance with the respective forces provided between the frame 22 of the rolling mill stand and the back-up rolls 16 and 18 for a first operation when the strip workpiece does not extend to the next succeeding stand and for a second operation when the strip workpiece does extend to the next succeeding stand, such that a net actual forward tension output signal V is supplied by the signal comparison circuit 68 in accordance with the actual forward tension in the strip workpiece 20. The signal comparison circuit 70 is operative to provide a tension error signal V in accordance with a desired forward tension in the strip workpiece 20 relative to the stand N and the actual forward tension in the strip workpiece relative to the stand N. Any tension difference is manifested by the error signal V supplied by the signal comparison circuit 70 shown in FIG. 2 and applied to the motor for the stand N or the motor for the stand N +1 to correct the inter-stand tension between the respective stands N and stand N +1. The control operation for the strip tension between the other illustrated tension providing stands and reel device 52 shown in FIG. 2, is substantially similar to that already described relative to stand N.

While a preferred embodiment of the present invention has been disclosed, it is to be understood that the invention is capable of various adaptations and modifications within the spirit of the present invention.

I claim as my invention:

1. In strip tension control apparatus for a rolling mill having a first stand and a second stand, with each stand including a frame and having top and bottom rolls between which the strip passes, the combination of force sensing means operative with said first stand and being positioned between said frame and at least one of said rolls of the first stand for providing a control signal that varies in accordance with the force between said frame and said one roll when the strip is passing between the top and bottom rolls of the first stand, signal providing means operative with said first control signal and being responsive to the strip being present between the rolls of the first stand and being responsive to the strip being present between the rolls of the second stand to provide a second control signal in accordance with the difference in said force prior to the strip being between the rolls of the second stand and after the strip is between the rolls of the second stand, and strip tension control means operative with at least one of said stands for controlling in accordance with the second control signal the tension in said strip passing between the first stand and the second stand.

2. In control apparatus for a rolling mill having a stand including a frame and two rolls between which a workpiece is passed and having a workpiece tension providing device, the combination of roll force sensing means positioned between said frame and one of said rolls for providing a control signal proportional to the roll force between said frame and said one roll when the workpiece is passed between said two rolls, workpiece parameter control apparatus operative with said stand and being responsive to said control signal for providing a first parameter signal when the workpiece is passing through said stand and not yet operative with the tension providing device and for providing a second parameter signal when the workpiece is passing through said stand and is operative with the tension providing device, signal comparison means responsive to each of said first parameter signal and said second parameter signal for providing a tension control signal, and tension control apparatus operative with at least one of said stand and said tension providing device for controlling the workpiece tension relative to said stand as a function of said tension control signal.

3. In control apparatus for a rolling mill having at least a first stand and a second stand, with each stand including a frame and having top and bottom rolls between which a workpiece passes, the combination of force sensing means operative with said first stand and being positioned between the frame and at least one of the rolls of the first stand for providing a control signal that varies in accordance with a predetermined force between said frame and said one roll when the workpiece is passing between the top and bottom rolls of the first stand, signal providing means operative with said first control signal and being responsive to the workpiece being present between the rolls of the first stand and being responsive to the workpiece being present between the rolls of the second stand to provide a second control signal in accordance with the difference in said predetermined force prior to the workpiece being between the rolls of the second stand and after the workpiece is between the rolls of the second stand, and rolling mill operation control means operative with at least one of said stands for controlling in accordance with the second control signal the passing of said workpiece between the rolls of said one stand.

4. In control apparatus for a rolling mill having a stand including a frame and two rolls between which a workpiece is passed and having a workpiece passage controlling device, the combination of roll force sensing means positioned between said frame and one of said rolls for providing a control signal proportional to a predetermined roll force between said frame and said one roll when the workpiece is passed between said two rolls, workpiece parameter signal means operative with said stand and being responsive to said control signal for providing a first parameter signal when the workpiece is passing through said stand and not yet operative with the workpiece controlling device and for providing a second parameter signal when the workpiece is passing through said stand and is operative with the workpiece passage controlling device, signal comparison means responsive to each of said first parameter signal and said second parameter signal for providing a tension control signal, and tension control means for controlling the workpiece tension relative to said stand as a function of said tension control signal.

5. In control apparatus for a rolling mill having a stand including a frame and a pair of rolls between which a workpiece is passed and having a workpiece tension providing device, the combination of force sensing means operative with said stand for providing a control signal proportional to a predetermined force relative to said stand when the workpiece is passed between said pair of rolls, workpiece parameter control apparatus operative with said stand and being responsive to said control signal for providing a first force component signal when the workpiece is passing through said stand and not yet operative with the tension providing device and for providing a second force component signal when the workpiece is passing through said stand and is operative with the ten sion providing device, signal comparison means responsive to each of said first force component signal and said sec- 8 0nd force component signal for providing an operation control signal, and rolling mill control apparatus operative with at least one of said stand and said tension providing device for controlling the passage of the workpiece relative to said stand as a function of said operaation control signal.

References Cited by the Examiner UNITED STATES PATENTS 1,988,930 1/1935 Winne 72--205 3,018,676 1/1962 Polakowski 72-205 3,188,841 6/1965 Wallace 729 3,194,036 7/1965 Canfor et a1 72205 CHARLES W. LANHAM, Primary Examiner. L. A. LARSON, Assistant Examiner. 

1. IN STRIP TENSION CONTROL APPARATUS FOR A ROLLING MILL HAVING A FIRST STAND AND A SECOND STAND, WITH EACH STAND INCLUDING A FRAME AND HAVING TOP AND BOTTOM ROLLS BETWEEN WHICH THE STRIP PASSES, THE COMBINATION OF FORCE SENSING MEANS OPERATIVE WITH SAID FIRST STAND AND BEING POSITIONED BETWEEN SAID FRAME AND AT LEAST ONE OF SAID ROLLS OF THE FIRST STAND FOR PROVIDING A CONTROL SIGNAL THAT VARIES IN ACCORDANCE WITH THE FORCE BETWEEN SAID FRAME AND SAID ONE ROLL WHEN THE STRIP IS PASSING BETWEEN THE TOP AND BOTTOM ROLLS OF THE FIRST STAND, SIGNAL PROVIDING MEANS OPERATIVE WITH SAID FIRST CONTROL SIGNAL AND BEING RESPONSIVE TO THE STRIP BEING PRESENT BETWEEN THE ROLLS OF THE FIRST STAND AND BEING RESPONSIVE TO THE STRIP BEING PRESENT BETWEEN THE ROLLS OF THE SECOND STAND TO PROVIDE A SECOND CONTROL SIGNAL IN ACCORDANCE WITH THE DIFFERENCE IN SAID FORCE PRIOR TO THE STRIP BEING BETWEEN THE ROLLS OF THE SECOND STAND AND AFTER THE STRIP IS BETWEEN THE ROLLS OF THE SECOND STAND, AND STRIP TENSION CONTROL MEANS OPERATIVE WITH AT LEAST ONE OF SAID STANDS FOR CONTROLLING IN ACCORDANCE WITH THE SECOND CONTROL SIGNAL THE TENSION IN SAID STRIP PASSING BETWEEN THE FIRST STAND AND THE SECOND STAND. 